Intracellular pH control mechanisms in the diabetic myocardium

Intracellular pH (pHi) regulation and the consequences of this regulation may play a crucial role during ischaemia and especially on reperfusion after an ischaemic episode. A significant decrease in Na+/H+ exchange activity was first demonstrated in papillary muscles isolated from hearts of diabetic rats, and recently confirmed in diabetic rat isolated ventricular myocytes. This depressed activity of one of the major pHi regulatory mechanisms may afford some protection against ischaemia/reperfusion injury. A protection was indeed observed in perfused hearts isolated from diabetic rats, in which there was a markedly improved recovery of contractility following ischaemia, comparable to that obtained with a pharmacological block of Na+/H+ exchange in normal hearts. This was associated with a markedly slower pHi recovery.